1. Technical Field
The present invention relates generally to an image transmission apparatus which establishes facsimile communication with a facsimile machine through a telephone line, and more particularly to an image transmission apparatus which includes a main facsimile unit connected to a telephone line and a sub-facsimile unit communicating with the main unit by radio.
2. Background Art
Japanese Patent First Publication No. 4-115762 teaches, as shown in FIG. 8, a conventional facsimile machine which consists of a main unit 100 and a sub-unit 200. The main unit 100 has a communication controller receiving a telephone signal through a telephone line 350. The sub-unit 200 has facsimile terminal equipment. The main unit 100 and the sub-unit 200 also have transceivers 112 and 202, respectively, for radio transmission therebetween. The transceiver 112 transmits facsimile information from a calling party's facsimile machine 300 along with an operating procedure signal to the transceiver 202. The transceiver 202 of the sub-unit 200 transmits an operating procedure signal to be sent to the facsimile machine 300 to the transceiver 112 of the main unit 100.
A communication condition between the facsimile machine 300 connected to the main unit 112 through the telephone line 350 and the sub-unit 200 connected to the main unit 100 depends upon a radio transmission condition between the main unit 100 and the sub-unit 200 as well as a telephone communication condition. Thus, even if the telephone communication condition is good, a communication failure may occur or a retry operation may be performed many times as long as the radio communication condition is unstable, thus resulting in an increase in wasteful use of the telephone line.